What is the difference between a nautical mile and a knot? Home Ocean Facts What is the difference between a nautical mile and a knot? What is the difference between a nautical mile and a knot? A nautical mile measures distance and a knot measures speed. This image focuses on the legend from a NOAA Nautical Chart. A nautical mile is based on the circumference of the earth, and is equal to one minute of latitude. It is slightly more than a statute (land measured) mile (1 nautical mile = 1.1508 statute miles ). Nautical miles are used for charting and navigating. A knot is one nautical mile per hour (1 knot = 1.15 miles per hour ). The term knot dates from the 17th century, when sailors measured the speed of their ship by using a device called a "common log." This device was a coil of rope with uniformly spaced knots, attached to a piece of wood shaped like a slice of pie. The piece of wood was lowered from the back of the ship and allowed to float behind it. The line was allowed to pay out freely from the coil as the piece of wood fell behind the ship for a specific amount of time.

When the specified time had passed, the line was pulled in and the number of knots on the rope between the ship and the wood were counted. The speed of the ship was said to be the number of knots counted (Bowditch, 1984). Search Our Facts FAQ: What is a knot? What is a nautical mile? Welcome to OnlineConversion.com What is a knot? What is a nautical mile? Knots and Nautical miles are good old navy terms. The nautical mile was based on the circumference of the earth at the equator. Since the earth is 360 degrees of longitude around, and degrees are broken into 60 so-called "minutes", that means there are 360 * 60 = 21,600 "minutes" of longitude around the earth. This was taken as the basis for the nautical mile; thus, by definition, 1 minute of longitude at the equator is equal to 1 nautical mile. So the earth is ideally, by definition, 21,600 nautical miles (and 21,600 "minutes" of longitude) in circumference at the equator.

If anyone ever asks you how far is it around the earth, you can quickly do the math in your head (360 degrees * 60 minutes per degree) and answer "about 21,600 nautical miles!" In fact, even modern navigators use the "minute of latitude" on charts to measure distance; this is what you see them doing when they use their compass spreaders while they are hovering over their nautical charts (maps). [For geometrical reasons, we use the minute of latitude on charts to correspond to a nautical mile rather than the minute of longitude. Minutes of longitude shrink as they move away from the equator and towards the poles; minutes of latitude do not shrink. Take a look at a globe with longitude and latitude lines marked on it to understand why.] Using the definition of a nautical mile for distance at sea, the challenge was to measure speed -- i.e. what is the ship's speed in nautical miles per hour?

(By the way, the nautical mile is about 1.15 larger than the "statute" mile used by land lubbers.) Since [speed] = [distance] divided by [time], if we measure a small distance (or length) in a small time we can do the math and figure our speed. The device that sailors used to make their speed measurement was called the "chip log." Chip as in chip of wood, and log as in to record in a log. The chip was a wedge of wood about 18" in size; it was tied to one end of a rope on a large spool. The rope had knots tied into it about every 47'3" (more about how that was calibrated below). The wooden chip was thrown overboard at the ship's stern (back end). Because of its wedge shape, it would "grab" the water and start pulling out rope as the ship moved forward at some yet unknown speed. One man would hold the spool of rope as it played out; another man would start a sandglass filled with 30 seconds of sand; and a third man would count the knots as they passed over the stern board.

When the 30 seconds of sand expired, the time keeper would call out and the counting of knots would stop. The faster the ship was sailing, more knots and a longer length of rope were played out. The number of knots in the rope that were counted in 30 seconds, then, was equal to the speed of the ship in nautical miles per hour. A "knot", therefore, is not a nautical mile, it is a nautical mile per hour. Thus 1 knot was equivalent to 1 nautical mile per hour; 5 knots were equivalent to 5 nautical miles per hour; etc. The similar sound of "knot" and "naut" is entirely coincidental. Finally, what about the actual values of 47'3" between knots on the rope and the 30 seconds that were used with the chip log? The length was based on converting [1 nautical mile per hour] to [feet per second(fps)], and then multiplying [fps] by 30 seconds (which was a practical time to spend counting knots with a sandglass). The result was the calibrated length in feet at which to tie the knots for a 30-second run of the chip log.

... Now that we have much more precise technology to measure things, and because we need to establish international standards and conversion factors, and because the earth is not uniformly flat or round anywhere, and because even the precise definition of the second has changed, the official value for how many international feet in an international nautical mile has changed. Likewise, the measuring time of about "30 seconds" in the sandglass is now calibrated at 28 seconds. Time itself didn't change by 6.7%! But the cumulative effects of new international standard definitions for time, feet, statute miles, and nautical miles and more accurate measurements of the actual size of the earth -- and the fact that we don't use sand to measure time anymore -- have changed the modern calibration of the chip log. For a photograph and brief explanation of the chip log, see [..link temporarily down..] "All hands to loose topgallant sails!" By Brian Hagerty, posted with permission. Nautical Miles - Seafaring Definition and History Nautical Miles The Development of Nautical Miles and Nautical Charts Gary John Norman/ Stone/ Getty Images By Amanda Briney Updated August 31, 2015.

A nautical mile is a unit of measurement used on water by sailors and/or navigators in shipping and aviation. It is the average length of one minute of one degree along a great circle of the Earth. One nautical mile corresponds to one minute of latitude . Thus, degrees of latitude are approximately 60 nautical miles apart. By contrast, the distance of nautical miles between degrees of longitude is not constant because lines of longitude become closer together as they converge at the poles. Nautical miles are typically abbreviated with the symbols nm, NM or nmi. For example, 60 NM represents 60 nautical miles. In addition to being used in navigation and aviation, nautical miles are also used polar exploration and international laws and treaties regarding territorial water limits . Nautical Mile History Until 1929, there was not an internationally agreed upon distance or definition for the nautical mile. In that year, the First International Extraordinary Hydrographic Conference was held in Monaco and at the conference, it was determined that the international nautical mile would be exactly 6,076 feet (1,852 meters).

continue reading below our video 4 Tips for Improving Test Performance Currently this is the only definition in use widely and it is the one that is accepted by the International Hydrographic Organization and the International Bureau of Weights and Measures . Prior to 1929, different countries had different definitions of the nautical mile. For example, the United States measurements were based on the Clarke 1866 Ellipsoid and the length of one minute of arc along a great circle. With these calculations, a nautical mile was 6080.20 feet (1,853 meters). The U.S. abandoned this definition and accepted the international measure of a nautical mile in 1954. In the United Kingdom , the nautical mile was based on the knot. A knot is a unit of speed derived from dragging pieces of knotted string from sailing ships. The number of knots falling into the water over a given period of time determines the knots per hour. Using knots , the U.K. determined that one knot was one nautical mile and one nautical mile represented 6,080 feet (1853.18 meters). In 1970, the U.K.

abandoned this definition of the nautical mile and now uses exactly 1,853 meters as its definition. Using Nautical Miles Today, one nautical mile still equals exactly the internationally agreed upon measure of 1,852 meters (6,076 feet). One of the most important concepts in understanding the nautical mile though is its relation to latitude. Because a nautical mile is based on Earth’s circumference, an easy way to understand the calculation of a nautical mile is to imagine the Earth being cut in half. Once cut, the circle of the half can be divided into equal portions of 360°. These degrees can then be divided into 60 minutes. One of these minutes (or minutes of arc as they are called in navigation) along a great circle on Earth represents one nautical mile. In terms of statute or land miles, a nautical mile represents 1.15 miles. This is because one degree of latitude is approximately 69 statute miles in length. 1/60th of that measure would be 1.15 statute miles.

Another example is travelling around the Earth at the equator to do this, one would have to travel 24,857 miles (40,003 km). When converted to nautical miles, the distance would be 21,600 NM. In addition to its use in navigational purposes, nautical miles are also still significant markers of speed as the term "knot" is today used to mean one nautical mile per hour. Therefore if a ship is moving at 10 knots, it is moving at 10 nautical miles per hour. The term knot as it is used today is derived from the previously mentioned practice of using a log (a knotted rope tied to a ship) to gauge the speed of a ship. To do this, the log would be thrown into the water and trailed behind the ship. The number of knots that passed off of the ship and into the water over a certain amount of time would be counted and the number counted determined speed in “knots.” Present-day knot measurements are determined with more technologically advanced methods however such as mechanical tow, Doppler radar, and/or GPS.

Nautical Charts Because nautical miles have constant measurement following lines of longitude, they are extremely useful in navigation. To make navigation easier, sailors and aviators have developed nautical charts which serve as a graphical representation of the Earth with a focus on its areas of water. Most nautical charts contain information on the open sea, coastlines, navigable inland waters and canal systems. Usually, nautical charts use one of three map projections : the gnomic, polyconic and Mercator. The Mercator projection is the most common of these three because on it, lines of latitude and longitude cross at right angles forming a rectangular grid. On this grid, the straight lines of latitude and longitude work as straight line courses and can easily be plotted through the water as navigable routes. The addition of the nautical mile and its representation of one minute of latitude make navigation relatively easy in open water, thus making it an extremely important component of exploration, shipping and geography. Knot Conversion Chart (Speed Converter, Nautical) Knot Conversion Chart This converter is very easy. Really. 1 This is a conversion chart for knot (Nautical). To switch the unit simply find the one you want on the page and click it. Enter the value you want to convert (knot).

Then click the Convert Me button. Your value gets instantly converted to all other units on the page. 3 Now find the unit you want and get the conversion result next to it. It's your answer. Type your knot value below. Touch "Convert Me" button. Could not find your unit? Try to search: Hope you have made all your conversions and enjoyed Convert-me.Com. Come visit us again soon! Knot conversion chart page, Speed units metric conversion. Copyright © 1996-2017 by Sergey Gershtein , Anna Gershtein . Unauthorized duplication prohibited. All rights reserved. Layout based on YAML Without the substance conversion to some units cannot be calculated. i Like convert-me.com and want to help? We appreciate it! Go ahead and let your friends know about us. Use the buttons on the top to share. Hint: Conversion questions? Try Convert-me.com forum where you can discuss them. Hint: You don't have to click "Convert Me" button every time. Hitting Enter or Tab key after typing in your value also triggers the calculations. Found an error? Want to suggest more conversions? Contact us on Facebook . Hint: Can't figure out where to look for your unit?

Try searching for the unit name. The search box is in the top right corner of the page. Has convert-me.com really existed since 1996? In fact it's even older. We launched the first version of our online units converter in 1995. There was no JavaScript there and all conversions had to be done on server. The service was slow. A year later the technology allowed us to create an instant units conversion service that became the prototype of what you see now. To conserve space on the page some units block may display collapsed. Tap any unit block header to expand/collapse it. Does the page look too crowded with so many units? You can hide the blocks you don't need by clicking on the block headline. Try it. Clicking again will expand the block. Our goal is to make units conversion as easy as possible. Got ideas how to make it better? Let us know . [x] Knots, Fathoms, and Gales: Nautical Measurements - boats.com Back to search results Knots, Fathoms, and Gales: Nautical Measurements No matter what kind of boating you enjoy, here’s how to understand the nautical expressions for speed, depth, and wind force.

By Lenny Rudow November 6, 2014 Whether you own a center console fishing boat, a jet boat , or a cruising sailboat , you’re a boater—a mariner, in nautical parlance. And boating is an activity that has a far longer history than most other recreational pastimes. As a result, we mariners have our own unique nautical language. We also have our own nautical ways of doing things. And yes, we even have our own nautical measurement systems. Naturally, this can be a bit confusing for those new to the fold. You highly-experienced, life-long mariners can now tune out. You’ll find the more advanced information you may be seeking in our Boat Maintenance and DIY section,or among our How-To articles and videos . For beginner boaters, however, here’s a crash-course in nautical measurements. Mariners have their own way of measuring things - and describing what those measurements mean. Photo: US Navy SPEED and DISTANCE While the rest of the world thinks in kilometers or miles per hour, boaters think in terms of knots.

A knot is one nautical mile per hour, and it’s equal to 1.151 statute (regular) miles per hour. We use nautical miles instead of statute miles because of basic navigation; the distance of one nautical mile corresponds to one minute of latitude on a chart. Long before GPS, paddlewheel speedos, and pitot tubes appeared on the scene, sailors needed a way to measure the speed of their boat. So they tied knots in a length of rope, one knot at every 47’3”, then tossed the end of the rope over the side of the boat and counted how many knots passed by in a 30 second period. We don’t need to get into the math, but you should get the general idea—the number of knots in the rope that passed overboard told the sailors how many nautical miles per hour they were going. Is this boat doing 70 knots, or is it going over 80 MPH? Yes. You may have noticed that in the performance section of many of our boat reviews, we actually show boat speed in statute miles per hour. Why?

This is a reflection of reality; most people think in terms of MPH these days, and most boaters have their GPS set to that increment. Here's how to convert one to the other: multiply MPH by 1.151 to get knots, and divide knots by 1.151 to get MPH. DEPTH Today, a fathom equals six feet—quite an inconvenient number to use in your head, when trying to go back and forth between feet and fathoms—but it was once used as a general term to mean the distance between a mans’ out-stretched arms. It might mean five feet, it might be five and a half, or it might be six. Fortunately, at some point a few hundred years ago, someone realized that six feet was almost exactly one-thousandth of a nautical mile (6,080 feet), so it made sense to standardize the term at that length. You can still find charts (or set those on your GPS/chartplotter) that use fathoms for depth readings, but other than a few select groups of mariners who spend lots of time far from shore, most people simply speak in terms of feet these days.

One exception: virtually all charts will show certain fathom “curves” (bathymetric lines) at a few specific increments: 20 fathoms (120 feet), 50 fathoms (300 feet), and 100 fathoms (600 feet). WIND FORCE Although wind is commonly expressed in MPH or knots, it’s also regularly identified by the terms set out in the Beaufort Scale. The Beaufort Scale is yet another remnant of times past, when measurements were often unequal and somewhat subjective. It came to us courtesy of Francis Beaufort, a Commander in His Majesty’s Navy in the early 1800's. (Read The Beaufort Scale: Judging the Wind in your Sails for a more complete history).

The scale uses terms to identify wind speeds, as follows: 0 knots of wind: calm 1 – 3 knots: light air 4 – 6 knots: light breeze 7 – 10 knots: gentle breeze 11 – 16 knots: moderate breeze 17 – 21 knots: fresh breeze 22 – 27 knots: strong breeze 28 – 33 knots: near gale 34 – 40 knots: gale 41 – 47 knots: strong gale 48 – 55 knots: storm 56 – 63 knots: violent storm 64 knots and above: hurricane There's a big difference between "blowing a gale," and a "fresh breeze:" Thirteen knots, to be exact. Even today, although NOAA’s official wind forecasts are given in speed, the general description at the beginning of the forecast often employs the terms of the Beaufort Scale. If a front is pushing through and 35 knot winds are expected, for example, the description might read “Gale winds are forecast…” Want to learn more of the basics about boating?

Be sure to also read: Knot measure of speed A speed measurement that is equal to one nautical View Full Document Knot (measure of speed). A speed measurement that is equal to one nautical mile per hour. One knot is equal to 1.15 statute mile per hour. Kollsman window. The barometric scale window of a sensitive altimeter. See barometric scale. Koroseal lacing. A plastic lacing material available in round or rectangular cross sections and used for holding wire bundles and tubing together. It holds tension on knots inde±nitely and is impervious to petroleum products. Kraft paper. A tough brown wrapping paper, like that used for paper bags. Labyrinth seal. A type of seal in a Roots blower cabin supercharger that is made in the form of knife edges riding in step-shaped grooves. Air pressure is dropped in each section of the seal, and any oil in the air is trapped in the grooves. Lacquer. A ±nishing material made of a ±lm base, solvents, plasticizers, and thinners. The ±lm base forms a tough ±lm over the surface when it dries.

The solvents dissolve the ±lm base so it can be applied as a liquid. The plasticizers give the ±lm base the needed resilience, and the thinners dilute the lacquer so it can be applied with a spray gun. Lacquer is sprayed on the surface as a liquid, and when the solvents and thinners evaporate, the ±lm base remains as a tough decorative and protective coating. Landing gear warning system. A system of lights used to indicate the condition of the landing gear. A red light illuminates when any of the gears are in an unsafe condition; a green light shows when all of the gears are down and locked, and no light is lit when the gears are all up and locked. An aural warning system is installed that sounds a horn if any of the landing gears are not down and locked when the throttles are retarded for landing. Laminar flow. Air²ow in which the air passes over the surface in smooth layers with a minimum of turbulence. Laminated wood. A type of wood made by gluing several pieces of thin wood together. The grain of all pieces runs in the same direction. Latent heat.

Heat that is added to a material that causes a change in its state without changing its temperature. Lateral axis. An imaginary line, passing through the center of gravity of an airplane, and extending across it from wing tip to wing tip. Lay-up. The placement of the various layers of resin- impregnated fabric in the mold for a piece of laminated composite material. L/D ratio. A measure of ef±ciency of an airfoil. It is the ratio of the lift to the total drag at a speci±ed angle of attack. Left-right indicator. The course-deviation indicator used with a VOR navigation system. This preview has intentionally blurred sections. Sign up to view the full version. View Full Document G-22 Lightening hole. A hole cut in a piece of structural material to get rid of weight without losing any strength. A hole several inches in diameter may be cut in a piece of metal at a point where the metal is not needed for strength, and the edges of the hole are Fanged to give it rigidity. A piece of metal with properly Fanged lightening holes is more rigid than the metal before the holes were cut. This is the end of the preview.

Sign up to access the rest of the document. TERM Chapter 14 Aircraft Fuel System Basic Fuel System Requirements All powered aircraft r ama_ch14_Fuel sys.pdf Nautical Units and Angles NAUTICAL UNITS AND ANGLES I must confess that I know nothing of sailing, so I hope that I haven't made too many mistakes in the following! Nautical distance and depth Full fathom five thy father lies; Of his bones are coral made: Those are pearls that were his eyes: Nothing of him that doth fade, But does suffer a sea-change Into something rich and strange. Shakespeare - The Tempest Fathoms measure depth. They have been in use since before 1600, and may be derived from "faethm", the Anglo Saxon word for "to embrace" (because it is roughly the distance from one hand to the other if your arms are out-stretched). Tim Chafer from Germany says "The English term is related to the German term 'Faden', which is also the general term for 'thread'.

A 'Faden' or 'fathom' would thus originally have been the length of rope or thread you could stretch between the hands with the arms outstretched." Nautical miles measure distance. 1 nautical mile is the angular distance of 1 minute of arc on the earth's surface. As these differ slightly (6108' at pole c.f. 6046' at equator) 6080 was adopted (this being it's approximate value in the English Channel). The International nautical mile is 1852 metres, so is very slightly different from the UK nautical mile. 1 UK nautical mile = 1.00064 international nautical miles Now the International nautical mile is used throughout the UK, except in the Statutory Instrument 1995 No. 1804 which defines it as 1853 metres! If you want an irrelevant fact, one minute of arc on Mars is close to a kilometre (.987 km to be more accurate). Perhaps the French who defined the kilometre were really Martians! A knot is a nautical measure of speed, one nautical mile per hour (or about 1.15 mph).

The name comes from the knots tied in the log line used with the sand glass. The log line was thrown onto the sea and the knots in the line were counted as they ran out during the sand glass interval. The knot has been used since the 17c. It is sometimes called the sea mile. Again, the international knot is very slightly less than the UK knot. The following information is given by Dick Grindley. "A cable was originally the length of (believe it or not) a hemp cable defined by the RN (although further complicated by whether it was a rope or a hawser laid cable), the shackle came later when anchor chains started being made of lengths of a number of un-dividable links joined up at a 'joining shackle'. So an anchor cable will always be an integral number of shackles long. In chart work the cable is still in use for the simple reason that charts are usually large & when you use them you tend to fold them to get at the bit you want. Having folded them the metric linear scale is never visible (must be someone's law ?) but at either side of the chart is the latitude scale in units of mins, sub-divided into 10 (a.k.a.

the cable). So, when I did my chart work training at Dartmouth (a few years ago I must admit) we quite happily mixed metric depth & height with nm & cables for distance." The shackle has given me some trouble. I've been given the values of 12 fathoms, 12.5 fathoms and 15 fathoms (which is the correct figure) to the shackle. I am indebted to Richard Sheppard for the following information: Apparently, according to a quote from a 19th Century Seamanship Manual, ships were usually equipped with 12 shackles of *bower cable* where each shackle was a 12.5 fathom length. (Perhaps this is where the figure of 12 comes from?) These 12.5 fathom lengths were joined by shackles (hence the name) and by swivel links to overcome twisting. When paying out the anchor cable, counting the number of shackles passing gave a measure of the length used. In 1949, the Royal Navy switched from 12.5 fathom shackles to 15 fathom shackles.

In 1970, the RN Hydrographic Charts Dept. switched their Nautical Mile from 6080 feet to 1852 metres (the International NM). At the same time, their Cable became a tenth of the International Nautical Mile. Modern heavy mooring chain is usually sold in 15 fathom lengths or *shots*. The specification sheets quote the number of links per shot. Much of it seems to come from the Far East! Light chain can be bought in arbitrary lengths. The Observer newspaper had a lot of trouble with the definition of a ship's tonnage. It appears in their readers' corrections column 3 weeks running. So for everyone else, here is their final definition: Tonnage is a measure of the internal volume of a ship, devised as a basis for charging habour dues. It is said to originate with 'tuns' of wine, one tun being equal to 252 gallons, roughly 42 cubic feet. The modern tonnage measurement, introduced by the Merchant Shipping Act 1854, is 100 cubic feet.

Gross tonnage is the internal volume of the ship and Net (or Register) is the Gross tonnage less non-earning spaces, such as engine room and crew accommodation. I had an email from 'an ex-Marconi seadog' who told me some nautical slang - nothing to do with units of measure but I can't resist it! Tab Nabs = light treats (food) Doby = clothes for washing - verb dobying - doby dust = washing powder. To put someone ON THE SHAKE = to wake them up Deck head survey = sleeping Points of the Compass Most people know the four main points of the compass, North, South, East and West (see left). If you can't remember which way round "West" and "East", they read "we"! However, there are 32 points of the compass. The best way to see this is to build it up a bit at the time. Half way between North and East is North East. This gives 8 points. The North or South always comes first, and the East or West comes second. Now, imagine half way between East and North East. This is called East North East. (You could think of it as East North-East).

The single point (North, South, East, West) comes first, and the double point (North East, North West, South East, South West) comes second. This makes sixteen points. Now imagine half way between each of these points. This makes up 32 points. To get the name of a point like this: take the nearest single or double name (such as North East). Then describe the movement to the new point by saying 'North East by North' to go anti-clockwise or 'North East by East' to go clockwise. So, starting from N and working clockwise, the points are: N, N by E, NNE, NE by N, NE, NE by E, ENE, E by N, E etc. I'm afraid I'm NOT going to illustrate this! As you can see, this is quite complicated. Now directions are given by degrees. North is zero, and the degrees go clockwise. So East is 90 degrees, and West is 270 degrees. This has the advantage that all bearings are equally simple, but it doesn't sound so romantic. While angles are, of course, not confined to the sea, they follow on from the previous subject.

There are 360 degrees in a circle (or 'full turn'). This is a useful figure, since it can be divided in many ways, so if you want to divide a round cake into 3, it's 120 degrees, 4 pieces are 90 degrees, 5 pieces are 72 degrees, 6 pieces are 60 degrees, and so on. One degree is a very small amount, but if you want something smaller, then there are 60 minutes to a degree, and 60 seconds to a minute. So there are 1,296,000 seconds to a circle! However, in Mathematics, we meet another way of measuring angles - radians. There are 2 pi radians to a circle, where pi is the ratio of the diameter of a circle to its circumference (round its edge). It should have its own symbol, but this might not work on all browsers, so I'm not using it. It looks like a minature Stonehenge.

It is a very strange number, approximately 3.1416, but however many places of decimals you write, you never reach the accurate figure of pi, and the number sequences never start to repeat themselves continually. This is called an irrational number, and pi is, perhaps, the most famous example. I am tempted to call mathematicians pretty irrational to use a unit where you not only don't get a whole number of them to a complete circle, you don't even get a rational number (or fraction)! They would defend themselvese by stating that if you cut a slice of cake with angle of one radian, then its rounded edge is the same length as its straight sides (or the radius of the original circle). There are also formulae which are easier to deal with if you use radians rather than degrees. Another angle unit is the mil. This is a military unit for defining angles. The name derives from milliradian, and they are used because an angle of X mils is X metres wide at a distance of X kilometres.

This means that if you drop a shell 200 metres to one side of the target (according to your map) and it's 4 km away, 200 divided by 4 is 50, so you swing your aim by 50 mils. Note that current OS maps have the magnetic and grid deviations shown in mils as well as degrees. There are 6283.1853 mils in a circle, but they seem to be rounded off to various values in use, such as 6283 and 6280. However, the US military made things 'simpler' by standardizing on 6400 mils in a circle. To make things even more interesting, the Russians, and perhaps others in Europe, use 6000 mils in a circle! Anyone who seriously disapproves of metric systems may be pleased to hear that the French Revolutionary lot tried to define a 'metric' angle of measurement. This was gradians, and there were 400 to a circle (so 100 to a right angle). It never caught on.

They also tried to define time as 20 hours to a day, and 100 minutes to an hour, with an equal lack of success. (I'm surprised that they didn't try to define 400 days to a year!) Jo Edkins was born in 1953 in England, and she learnt her tables at school as did all children of that time. This included not only the multiplication tables, but Lengths and Measures as well, and these were usually to be found at the back of our exercise books. All people of around that age know vaguely about 'rods, poles and perches' even if they can't remember what they are! However, when Jo's son was born, children were only taught metric, and Lengths and Measures became boring powers of ten. Jo thought it was a shame that this information should die out altogether, so she looked it up in various ancient and falling-to-pieces reference books, and put it in a website.

This website has been greatly expanded by many people writing to her with additional information (and corrections where she's made mistakes!) Jo has no experience of sailing, boats or ships at all (apart from punts), and has lived over a hundred miles from the sea for most of her life - quite hard to do in England! However, she loved the Swallows and Amazons books of Arthur Ransom as a child, and added a page on Nautical measurements and Angles, and another on Weather, to her website. This has been expanded by other people's contributions. Choose Topic (Column 2): The Sailing Club - Measurement The Sailing Club, Inc. Measurement The great thing about the English system of measure versus the SI (or metric) system is that there are so many ways of measuring things. On this page, we provide definitions of some of the common and uncommon measures used onboard. Commonly Used Units of Measure Fathom A measurement of length equal to 6 feet. Often used to describe depth.

"In running along shore we shoald in our water from 9 to 7 fathom and at one time had but 6 fathoms which determined me to anchor for the night." -- The Endeavor Journal of James Cook 22 May 1770. Knot A measure of speed equal to one nautical mile per hour. It is considered by many to be incorrect usage to say, "knots per hour." Derived from original measuring device in which a piece of wood was attached to a line with knots tied at regular intervals. When the wood was tossed overboard, the number of knots passing in a given period of time recorded the speed. "Having for some time past generally found the Ship by Obsern to the Northward of the Logg, which is not owing to a current as I at first imagined but to a wrong division of the Log line being 2 1/2 feet in each knot; but this is now rectified." -- The Endeavor Journal of James Cook 12 February 1769. Nautical Mile A measure of length based on one minute of latitude.

Since latitude varies with longitude (the earth isn't a perfect sphere), the International Hydrographic Organization adopted 1852 meters or 6076.12 feet as the international nautical mile. Less Commonly Used Units of Measure Cable A measure of length equal to one tenth of a nautical mile. Approximately, 100 fathoms. "At 9 oClock being little wind and variable we were carried by the Tide or current within 2 Cable lengths of the NW shore where we had 54 fathoms water, but with the help of our Boats we got her Clear." -- The Endeavor Journal of James Cook 15 January 1770. Hank Loops of rope. Small stuff (thin diameter line) is often sold by the hank. Actual length is variable, lengths of 50 or 100 feet are common. Fore and Aft sails were originally tied to stays using small pieces of line, hence the expression "hanking on a sail." For those who avoid roller furling jibs, the pieces of hardware used to attach the jib to the forestay are called hanks.

League At sea, a measurement of length equal to 3 nautical miles. (Also called a nautical league.) "At day light in the Morning we made sail Cape Manifold bearing South-by-East distant 8 Leagues" -- The Endeavor Journal of James Cook 28 May 1770. Shot A measurement of length equal to 15 fathoms (90 feet) in the U.S. and 12.5 fathoms (75 feet) in Great Britain. Almost always refers to a measurement of chain. Span A measurement of length equal to about nine inches. Taken from the distance between the tip of the thumb and the tip of the little finger in a fully extended hand. Why is a ship’s speed measured in knots? - Ask History Ask History May 14, 2014 By Elizabeth Nix Share this: Why is a ship’s speed measured in knots? Author Why is a ship’s speed measured in knots? URL Google Ancient mariners used to gauge how fast their ship was moving by throwing a piece of wood or other floatable object over the vessel’s bow then counting the amount of time that elapsed before its stern passed the object.

This method was known as a Dutchman’s log. By the late 16th century, sailors had begun using a chip log to measure speed. In this method, knots were tied at uniform intervals in a length of rope and then one end of the rope, with a pie-slice-shape piece of wood (or “chip”) attached to it, was tossed behind the ship. As the vessel moved forward, the line of rope was allowed to roll out freely for a specific amount of time, which was typically tabulated with an hourglass. Afterward, the number of knots that had gone over the ship’s stern was counted and used in calculating the vessel’s rate of speed. A knot came to mean one nautical mile per hour. Therefore, a ship traveling at 15 knots could go 15 nautical miles per hour. For a number of years, there was disagreement among various nations about the exact measurement of a nautical mile, which is based on the Earth’s circumference. In 1929, the international nautical mile was standardized at 6,076 feet; it was adopted by the United States in 1954.

A nautical mile is different from a mile on land, which is based on walking distance. The Romans first defined a land mile as 1,000 paces or pairs of steps; it was set at its current measurement of 5,280 feet by Queen Elizabeth I in 1593. Tags

Question: What is the nautical measurement of speed equal to one nautical mile per hour?
Answer: Knot